Short wave length electric lamp



y 9, 1935. S.-RUBEN 2,007,924

7 SHORT WAVE LENGTH ELECTRIC LAMP Filed Aug. 25, 1930 2 Sheets-Sheet 1July 9,1935. 5, RUBEN SHORT WAVE LENGTH ELECTRIC LAMP 7 Filed Aug. 25.1930 2 Shets-Sheet 2 INVENTQR ATlfORNEY Patented July 9, 1935 I UNITEDSTATES PATENT OFFICE SHORT WAVE LENGTH ELECTRIC LAMP Saniucl Ruben, NewRochelle, N. Y., assignor to Sirian Lamp Company, Newark, N. J., acorporation of Delaware Application August 23, 1930, Serial No. 477,306

6 Claims. (Cl. l'lfi l) diation which have been available aresun-light,

the arc-light, and the mercury vapor lamp. The sun-light is too variableto be considered industrially. Arc lights are also variable in operationand costly to operate due to the continual consumption of the-electrodematerial. Mercury vapor lamps besides having a high initial cost requiredirect current for operation and have a short life due to consumption ofthe electrode surface. These also require auxiliary equipment.

It is one of the objects of the present invention to provide a shortwave length electric light which may be operated on commercial circuitswithout any auxiliary equipment and with low power consumption and longlife.

Another object of the invention is to provide a device for. producingshort wave length light which arises from a uniform electrical dischargev with high intensity and the steadiness of a fila- 25 ment.

Another object of the invention is to provide a short wave length lightwhich may be operated on commercial lighting circuits and which is madeup like an ordinary light bulb so that it may be screwed into anystandard socket.

Other objects of the invention and objects ;relating to the constructionand assembly of the various parts will be apparent as the descriptionthereof proceeds.

The invention has been illustrated in the accompanying drawings inwhich:

Fig. 1 is a side elevational view of one embodiment of my improved lowwave length electric light;

Fig. 2 is a longitudinal enlarged view partly in section of one end ofone of the lighting elements;

Fig. 3 is a side-elevational view of a modified form of the invention;and

Fig. 4 is a sectional plan view of the construction shown in Fig. 3taken on the line 3-4 of Fig. 3.

Referring now more specifically to the drawings the construction of thelamp shown in Fig. 1 comprises an envelope lll preferably of quartzglass, borosilicate, or other material which will not absorb short wavelength radiation to an appreciable extent and which may be formedintegral with a press II for supporting the various elements of thelamp. A straight support rod l2, may be sealed in the press II and mayextendupwardly 'may have its upper end attached to the support l3 Thisdrives out the binder in the electron emitto a point adjacent the top ofthe envelope where it may be bent at right angles to form a support l3for the light emitting element. A glass tube ll may be provided aroundthe support l2 extending between the-press H and the angular portion l3.5 Another support rod I5 may be sealed in the other side of the press Il and may be bent outwardly and upwardly terminating a short distancefrom the press. An electron emitting element I6 while its lower endmaybe attached to the short connector ll of nickel or other conductingmaterial. A second electron emitting element l8 may have its upper endconnected to the other end l of the connector l1 while its lower end maybe 1 5 connected to a second short connector I9 similar to theconnnector ll. Also a third electron emitting element 20 may have itsupper end connected to the upper end of the connector I!) and its lowerend connected to the' support rod l5 thus 20 placing all three electronemitting elements l8, i8, and 20 in series. All of these electronemitting elements may comprise a coil 2| (see Fig. 2) which may beformed of any desired resistance metal such as molybdenum, tungsten,tantalum, 25. or nichrome wound in a relatively small coil and havingthe outer surface of the coil coated with an electron emitting material22 which maybe any of the well known materials used for that purposesuch as the oxides of the alkaline earth metal group or any desiredmixtures of the oxides or any other material which will have ahighelectron emission efliciency at relatively low 'temperatures.

With the elements constructed as shown in the figure the envelope I0 maybe connected by means of a tube in the usual manner to an exhaust pumpand an oven placed over it to raise the temperature thereof to 350 to400 C. A curably be obtained. When no more gas is found in the bulb thecurrent may be increased through the filament so that the temperature isslowly raised to aboutv 800 C. with a bright red color.

ting material and other occluded gases which mi ht be present, thevacuum pump withdrawing thesev gases as they are driven out.

When the high vacuum is again obtained the oven may be raised and thefilament heated again for a moment to slightly less than 1200 C. todrive out more gases which are immediately removed from the envelope bythe vacuum pump. Then the pump may be shut off and the current turnedoff and a slight amount of an inert gas, such as neon at about mm.pressure, may be admitted to the bulb and the filament current turned onagain and gradually increased. Spots of localized discharge having areddish'color will then appear on the elements or support wires and willgradually spread till a diffused glow completely fills the bulb. Thisprocess activates the electron emitting coating and may be maintaineduntil the discharge is uniform throughout the entire bulb which usuallytakes less than ten minutes. During this time the current on thefilament should not be raised too high so that the coating on thefilament will not be destroyed or thrown off from the filament. If whitedischarge spots appear on the filament or support rods it is anindication that there are more gases or vapors within the bulband thebulb should again be exhausted and the whole process of activationrepeated.

When the activation is completed the filament temperature may be raisedfor a moment to about 1400" C. and then the vacuum pump again connectedand the gas pumped out to remove any undesirable gases which may havebeen thrown off during the activation process. The pump may then beturned off and about 5 mm. of helium gas and 10 mm. of neon may be addedto increase the conductivity to cause the discharge to occur in alldirections. Then enough argon gas may be added until all ionic dischargestops except an intense one around the filament and in the samedirection as the filament. This discharge will vary with the lightintensity and the temperature of the emitting oxides. About mm. of argonhas been found to be sufiicient to confine the ionic discharge along thelength of the filament. The bulb may then be sealed off.

A metal vapor may be introduced into the bulb by providing a smallcontainer 25 formed of metal plates and supported by a rod 26 which maybe welded to one'of the support rods, as the rod l6, and placed down inthe neck of the tube where it may be heated independently of the otherelements. In the container I may provide a small amount of magnesium anda salt preferably a chloride of one of the metals desired to be used inthe bulb. When the magnesium is fiashed after the bulb is sealed off toclean up the interior of the bulb it reacts with the metal saltliberating the free metal which condenses on the walls of the bulb. Thuswhere I desire to use mercury vapor in the bulb I provide mercuricchloride and magnesium in the container and when flashed the mercury isliberated leaving magnesium chloride which is stable and does notinterfere with the operation of the lamp. The

- mercury condenses on the walls of the envelope and evaporates againwhen the envelope is heated when the lamp is used.

Mercury vapor used in connection with argon as described above producesan ultra-violet light which is absolutely steady and has nodeteriorating effect upon the elements or other parts of the bulb. Otherradiations may be produced if desired by using calcium, caesium, orrubidium va- -tance material.

por with the helium, the mixture of rubidium and argon giving aninfra-red radiation. Not only is the discharge intense and practicallyuniform without any deterioration of the filament or coating but thetemperature of the filament is maintained relatively low and the lightis greatly increased over anything heretofore known or used.

When the leading-in wires 23 and 24 are connected-across the lightingcircuit the temperature of the electron emitting elements I6, l8, and 20is raised and the emission of electrons from these elements apparentlycauses ionization of the gas in the immediate vicinity thereof whichproduces a conductive path along the element and permits current to flowthrough this conductive path forming a discharge or halo which producesthe illumination.

Where I use the lamp on volts pressure I may prefer to use the threeseparated elements shown but a single element may be used if desiredwith lower voltages.

Note should be made of the fact that the glass tube M on the rod 12extends to the press II. This prevents any tendency to arc between thelower end of the element 20 and the opposite potential rod l2 andnecessitates any arcing tendency to be along the length of the elementand as this length is divided into three parts there is a third of thepotential difference across each individualelement and arcing isprevented.

While I have shown three separate elements it will be understood thatitmay be possible to use a single coil filament extending from the supportl5 to the straight portion I3 of the rod [2, and although I have showncoil filaments it may be preferable to use single straight wires ofresis- I may prefer to use the coil in order to increase the potentialdrop per unit length of element.

I may desirev to reflect the short wave length light in a givendirection and if so the construction of. Fig. 3 may be used. Here theenvelope 2! may be supported on the press 28 which contains support rods29 and 30 similar to the support rods I 2 and I 5 already described anda plurality of electron emitting elements 3|, 32, and 33 may beconnected between the support rod 30 and the upper end 29' of thesupport rod 29 in a manner similar to that already described with aheavy conductor 34 between the elements 3| and 32, and another 35between elements 32 and 33. This construction is similar to theconstruction of Fig. 1 except that the upper end 29 of the support rod29 may be made somewhat longer than the end l3 of the support rod l2 toprovide a greater space between the elements and the glass rod 36 whichcovers the support rod 39. Between the elements and the support rod Imay provide a. curved reflector 31 made of aluminum which has beenelectrolytically oxidized on its inner surface. Aluminum is preferredbecause it appears to be one of the best reflectors of short wave lengthlight when electrolytically oxidized. The aluminum reflector may beprovided with a pair of nickel eyelets 38 at the lower ends thereofwhich may be welded to two support rods 39 and 40 which may extenddownwardly and may be sealed in the press.

The reflector may be electrolytically oxidized by using it as the anodein an electrolytic bath of about 3% of borax and 10% of boric acidmaking about a 10% solution of the mixture in water. Two hundred voltsmay be applied across the circuit and about of an ampere per squarecentimeter of aluminum surface with the electrolyte at about 80 C.

While th invention has been shown and described in onnection with aparticular type of electron emitting element it is evident that otherelements may be used such as a single filamentary wire coated withelectron emitting material or such a. wire or a coil coatedintermittently may be used. .A coil of resistance wire may also haveindividual turns coated with the material if desired.

Many modifications of the invention may be resorted to without departingfrom the spirit I thereof, and I do not therefore desire to limit myselito what has been shown and described except as such limitations occur inthe appended claims.

What I desire to claim is:

1. In an electric lamp comprising an envelope, an electron emittingelement containing an oxide of the alkaline earth metals, means tosupport one end of said element, means to support the other end of saidelement, a glass tube sub,- stantially completely covering said lastmentioned means, and an ionizable gas surrounding said element andhaving a pressure and breakdown potential of such value as to confinethe ionization thereof to the region of said element when said elementis energized.

2. An electric lamp comprising an envelope, a high resistance electronemitting element containing an oxide of the alkaline earth metals, meansto support one end oi! said element, means to support the other end ofsaid element, means to substantially completely insulate said lastmentioned meansfrom gaseous discharge irom said first mentioned means,and an ionizable gas at a pressure of approximately 200 mm.

, ot mercury surrounding said element, said gas having a breakdownpotential along said element below that in the element necessary toraise the element to electron emitting temperature.

3. An electric lamp comprising an envelope, a

. high resistance electron emitting element containing an oxide 0tthealkaline earth metals,

means to support one end of said element, means to support the other end0! said element, means to substantially completely insulate said lastsaid first mentioned means, and an ionizable gascontaining mercury vaporsurrounding said element and having a pressure and breakdown po tentialsuch that the ionization thereof is confined to the region of saidelement when said element is energized.

4. An electric lamp comprising an envelope, a high resistance electronemitting element containing an oxide of the alkaline earth metals, meansto support one end of said element, means to support the other end ofsaid element, means to substantially completely insulate said lastmentioned means from gaseous discharge from said first mentioned means,and an ionizable gas containing mercury vapor surrounding said elementand having a pressure of substantially 200 mm. of mercury, said gashaving a breakdown potential along said element below that potential inthe element necessary to raise the same to electron emittingtemperature.

5. An electric lamp comprising an envelope, a plurality oi electronemitting elements connected in series, a plurality of low resistanceconductors, one connected between every two of said elements, means) tosupport the free end of the end electron emitting element, means tosupport the free end of the opposite end electron emitting element, atube of insulating material surrounding one of said last mentioned meansand substantially completely insulating it from the first means, and anionizable gas containing mercury vapor surrounding said elements andhaving a pressure of substantially 200 mm. of mercury.

6. An electric lamp comprising an envelope, a plurality of electronemitting elements connected inseries, a low resistance conductor betweenevery two of said elements, means to support the free'end of the endelement, means to support the, free end of the element on the other end,

means to substantially completely insulate said SAMUEL RUBEN.

1 substantially 200 mm.

